1. Field of the Invention
This invention relates to a camera having a camera-shake detecting circuit which is arranged to detect a camera shake by means of a camera-shake sensor.
2. Description of the Related Art
There has been proposed a camera which is arranged to obtain a camera-shake threshold time value on the basis of, for example, an image signal produced by a light receiving sensor by receiving the light of an object image and to take a photograph by setting a shutter speed at the camera-shake threshold time value thus obtained.
According to the prior art arrangement, however, it is impossible to know, before a shot, whether or not a set shutter time value is a time value which has been determined on the basis of the result of detection of a camera shake. Therefore, a shot might be taken on an erroneous assumption that the shutter time has automatically been set at a time value at which no blur of picture is caused by the camera shake. In cases where a camera-shake threshold time value is to be obtained by detecting an image signal as mentioned above, the image signal must be highly reliable. Therefore, the camera-shake threshold time value cannot be obtained in cases where the reliability of the image signal obtained by the sensor is low. However, it has been impossible to know the reliability of the image signal before taking a shot in accordance with the conventional arrangement.
Further, in the event of a low degree of luminance, the aperture of the lens of the camera must be shifted toward its maximum position for obtaining a correct exposure. However, if, in that event, the camera-shake threshold time value detected is a high shutter speed time, it might be impossible to obtain any correct exposure by shifting the aperture toward the maximum aperture. In such a case, the set shutter time must be shifted to a lower speed value. Therefore, in such a case, the shutter time which has been set at the camera-shake threshold time value by a camera-shake detecting action is automatically shifted to a lower shutter speed value. Under such a condition, a shot tends to be taken in an erroneous belief that the shot is to be taken at the camera-shake threshold time value.
Further, in cases where a shutter time value is arranged to be displayed in computing the camera-shake threshold time value, the camera-shake threshold time value becomes no longer obtainable if the reliability of the image signal lowers too much for detection. It is conceivable to solve this problem by making the display blank. However, making such a blank display every time an undetectable state occurs tends to make the shutter time display unstable. Besides, the conventional method requires a long period of time before completion of the camera-shake detecting action. If the shutter time display is left blank during the long detecting process, it would make the photographer feel uneasy.